Reuters: A massive oil spill in the Gulf of Mexico is unfolding just as the U.S. Senate was on the verge of considering climate change legislation that included an expansion of offshore oil drilling. The bill, which aims to reduce U.S. emissions of carbon dioxide and other greenhouse gases linked to global warming, already faced many political difficulties in the Senate. Some senators hate the bill’s plan to establish a new Wall Street trading system for pollution permits. Their opposition may …